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Transcript
Chapter 4
Companion site for Light and Video Microscopy
Author: Wayne
FIGURE 4.1
A simple microscope placed in front of the eye increases the visual angle, thus producing an enlarged
image of a microscopic specimen on the retina. The specimen appears to be located at the near point
of the relaxed eye and magnified.
Companion site for Light and Video Microscopy. by Wayne
Copyright © 2009 by Academic Press. All rights reserved.
2
FIGURE 4.2
Each objective is labeled with an abundance of useful information.
Companion site for Light and Video Microscopy. by Wayne
Copyright © 2009 by Academic Press. All rights reserved.
3
FIGURE 4.3
Chromatic aberration means that the focal length of an objective lens is wavelength dependent. There
is a large variation in focal lengths with wavelength in aspheric objectives, a smaller variation in
achromatic objectives, an even smaller variation in apochromatic objectives, and the smallest variation
in superachromatic objectives.
Companion site for Light and Video Microscopy. by Wayne
Copyright © 2009 by Academic Press. All rights reserved.
4
FIGURE 4.4
Chromatic aberration is reduced by building an objective lens with additional achromatic doublets and
triplets.
Companion site for Light and Video Microscopy. by Wayne
Copyright © 2009 by Academic Press. All rights reserved.
5
FIGURE 4.5
The cover glass introduces spherical aberration. The higher-order diffracted rays are refracted more
than the lower-order diffracted rays, resulting in the point being imaged as a zone of confusion. This
occurs because the lower order-diffracted rays appear to come from a position close to the object and
the higher order-diffracted rays, when they are traced back through the cover glass, seem to come
from a position between the real object position and the objective lens. The greater the cover glass
thickness, the greater the amount of spherical aberration that will be introduced by the cover glass. A
correction for the spherical aberration introduced by an objective lens also corrects the spherical
aberration introduced by a cover glass of a certain thickness (e.g., 0.17 mm). Objectives with
correction collars can correct for the spherical aberration introduced by a range of cover glass
thicknesses.
Companion site for Light and Video Microscopy. by Wayne
Copyright © 2009 by Academic Press. All rights reserved.
6
FIGURE 4.6
A negative ocular (A) has the field diaphragm between the eye lens and field lens. A positive ocular (B)
has the field diaphragm in front of the field lens.
Companion site for Light and Video Microscopy. by Wayne
Copyright © 2009 by Academic Press. All rights reserved.
7
FIGURE 4.7
Lens elements in sub-stage condensers. An Abbe chromatic sub-stage condenser (A), an aplanatic
sub-stage condenser (B), and an achromatic sub-stage condenser (C).
Companion site for Light and Video Microscopy. by Wayne
Copyright © 2009 by Academic Press. All rights reserved.
8
FIGURE 4.8
Paths of the illuminating rays (A) and the image forming rays (B) in a microscope set up with Köhler
illumination. The conjugate aperture planes are shown in (A) and the conjugate field planes are shown
in (B).
Companion site for Light and Video Microscopy. by Wayne
Copyright © 2009 by Academic Press. All rights reserved.
9
FIGURE 4.9
The lamp is placed at the center of curvature of a concave mirror to capture the backward-going light.
The collecting lenses focus an image of the filament onto the aperture plane at the front focal plane of
the sub-stage condenser.
Companion site for Light and Video Microscopy. by Wayne
Copyright © 2009 by Academic Press. All rights reserved.
10
FIGURE 4.10
Light emanating from all the points in the plane of the aperture diaphragm give rise to a converging set
of plane waves. The angle of each plane wave relative to the optical axis of the microscope is a
function of the distance of the point giving rise to the plane wave from the optical axis.
Companion site for Light and Video Microscopy. by Wayne
Copyright © 2009 by Academic Press. All rights reserved.
11
FIGURE 4.11
Together, the sub-stage condenser and the objective lenses produce an image of the filament at the
back focal plane of the objective.
Companion site for Light and Video Microscopy. by Wayne
Copyright © 2009 by Academic Press. All rights reserved.
12
FIGURE 4.12
The sub-stage condenser focuses an image of the field diaphragm onto the focused specimen. Each
and every point of the filament contributes to illuminating each and every point on the field diaphragm
and the specimen.
Companion site for Light and Video Microscopy. by Wayne
Copyright © 2009 by Academic Press. All rights reserved.
13
FIGURE 4.13
The objective lens produces an intermediate image of the specimen and the field diaphragm at the
field plane of the ocular. If the objective is marked with a 160 or 170, the field plane is 160 or 170 mm
behind the objective. If the objective is marked with an , the objective lens produces an intermediate
image at infinity and a tube lens is inserted so that the intermediate image is produced at the field
plane of the ocular.
Companion site for Light and Video Microscopy. by Wayne
Copyright © 2009 by Academic Press. All rights reserved.
14
FIGURE 4.14
The intermediate image is formed between the focal plane and the eye lens of a Ramsden ocular.
Together, the eye lens and the eye produce a real image of the specimen, any reticle in the ocular and
the field diaphragms on the retina. Without the eye lens, the visual angle of the intermediate image
would be tiny. With the eye lens, the visual angle is large and we imagine that we see the specimen
enlarged 25 cm from our eye.
Companion site for Light and Video Microscopy. by Wayne
Copyright © 2009 by Academic Press. All rights reserved.
15
FIGURE 4.15
Adjusting the field diaphragm changes the size of the field and adjusting the aperture diaphragm
changes the angle of illumination.
Companion site for Light and Video Microscopy. by Wayne
Copyright © 2009 by Academic Press. All rights reserved.
16
FIGURE 4.16
Depth of field.
Companion site for Light and Video Microscopy. by Wayne
Copyright © 2009 by Academic Press. All rights reserved.
17
FIGURE 4.17
Out-of-focus contrast in an invisible object. The waves coming from the closely spaced points s1 and
s2 in a transparent image interfere below the image plane to provide enough contrast to make the
nearly-faithful, out-of-focus image visible.
Companion site for Light and Video Microscopy. by Wayne
Copyright © 2009 by Academic Press. All rights reserved.
18